Final answer:
A chemical reaction occurs when new substances are formed from the rearrangement of atoms and bonds.
Step-by-step explanation:
In a chemical change, new substances are formed. In order for this to occur, the chemical bonds of the substances break, and the atoms that compose them separate and rearrange themselves into new substances with new chemical bonds. When this process occurs, we call it a chemical reaction. A chemical reaction is the process in which one or more substances are changed into one or more new substances.